Early Pregnancy Lifestyle and Glucose Patterns: A Substudy of TOFFFY

Continuous glucose monitor (CGM) will be used to assess 24-hour glucose exposure, expressed as area under the curve (AUC) (unit: mmol/L h). Higher AUC values indicate greater overall glucose exposure and poorer glycemic control.

CGM will be used to assess mean nocturnal glucose levels during the sleep period. The ideal nocturnal glucose range is 3.9-10mmol/L). Higher values indicate poorer nocturnal glycemic control.

CGM will be used to assess glycemic variability using the standard deviation (SD) of glucose values (unit: mmol/L), reflecting the dispersion from the average blood glucose level. Higher values indicate greater glycemic variability and poorer glycemic control.

CV is an accepted index for evaluating within-day glycemic variability, where CV = (SD) / (mean glucose) × 100%. Higher values indicate greater glycemic variability and poorer glycemic control. A CV of ≥36% is commonly used to define high glycemic variability.

Wrist actigraphy will be used to derive RAR by calculating the intra-daily variability (IV). IV reflects the degree of fragmentation in circadian activity patterns by assessing fluctuations in activity frequency and intensity within a given time period, capturing the extent of transitions between periods of rest and activity over time. IV values range from 0 to 1. Higher IV scores indicating poorer outcomes with greater disruption and fragmentation of the RAR.

Wrist actigraphy will be used to derive RAR by calculating the inter-daily variability (IS). IS reflects the stability of 24-hour circadian activity variations and the balance between RAR and the circadian cycle. IV values range from 0 to 1. IS values close to 1 indicating a better RAR outcome with greater rhythm stability.

AI-based food logging will be used to assess meal timing, defined as the timing of caloric intake, expressed as clock time of energy consumption. Later or more irregular intake timing indicates less favorable chrononutrition alignment.

AI-based food logging will be used to assess eating jetlag, defined as the difference in timing of the caloric midpoint between weekdays and weekends (unit: hours). Higher values indicate greater circadian misalignment in eating behavior.

AI-based food logging will be used to assess frequency of night-eating episodes, defined as the number of eating events occurring during the biological night or habitual sleep period. Higher night-eating frequency indicates poorer chrononutrition behavior.

Glucose tolerance status will be assessed using a 75 g oral glucose tolerance test (OGTT), which reflects dynamic glucose response at 0, 60, and 120 minutes (unit: mmol/L). Higher values indicate poorer glucose tolerance.

The glycemic outcomes will be compared between participants receiving the pilot intervention and those receiving usual care.

Total glycemic exposure during the 75 g OGTT will be calculated as area under the glucose curve (unit: mmol/L h). Higher values indicate poorer glucose tolerance.

The glycemic outcomes will be compared between participants receiving the pilot intervention and those receiving usual care.

Serum insulin concentration measured in blood (unit: pmol/L, SI unit) following the 75 g OGTT at 0, 60, and 120 minutes. Higher values indicate greater circulating insulin levels. The glycemic outcomes will be compared between participants receiving the pilot intervention and those receiving usual care.

C-peptide concentration is assessed (unit: pmol/L, SI unit) following the 75 g OGTT at 0, 60, and 120 minutes. Higher values indicate increased endogenous insulin secretion. The glycemic outcomes will be compared between participants receiving the pilot intervention and those receiving usual care.

HOMA-IR is derived from fasting glucose and fasting insulin to measure insulin resistance. Higher values indicate more insulin is needed to maintain glucose levels.

The glycemic outcomes will be compared between participants receiving the pilot intervention and those receiving usual care.

HOMA-β is derived from fasting glucose and fasting insulin to assess the function of beta cells in the pancreas, which are responsible for producing insulin. Higher value indicates better beta-cell functionality, while a lower value suggests impaired beta-cell function, which can be a sign of insulin resistance or diabetes.

The glycemic outcomes will be compared between participants receiving the pilot intervention and those receiving usual care.

Wrist actigraphy will be used to assess sleep timing, including sleep onset time and wake time (unit: clock time, hh:mm). Later sleep timing indicates delayed circadian phase. Changes across the monitoring period will be evaluated to assess potential behavioral effects of real-time self-monitoring.

Wrist actigraphy will be used to assess physical activity pattern based on daily step counts. Higher values indicate greater physical activity levels. Changes across the monitoring period will be evaluated to assess potential behavioral effects of real-time self-monitoring.